How can obesity or dehydration affect vein selection and sample quality?

• A. Veins are easier to palpate and dehydration reveals veins better
• B. Veins may be harder to palpate, and dehydration can make veins less visible; choose appropriate site and technique
• C. They do not affect vein selection
• D. They always require a different lab order

Answer: (B)

Obesity and dehydration change how easily a vein can be felt or seen, which influences where you puncture and how you perform the draw. In someone with obesity, veins often lie deeper and are harder to palpate, so choosing a more accessible site and using a careful technique becomes important. Dehydration reduces venous filling, making veins less visible and more difficult to access, which again means selecting the best available vein and adjusting the technique to minimize attempts. The goal is to pick a suitable site and use an appropriate technique to maintain sample quality and reduce the need for multiple sticks.